This invention relates to bonding of fully-fabricated semiconductor devices onto other fully-fabricated semiconductor devices so as to produce integrated units, and particularly to bonding fully-fabricated photonic elements, such as GaAs/AlGaAs multiple quantum well (MQW) modulators, onto fully-fabricated integrated circuit (IC) chips such as Si or even GaAs.
Integration of photonic devices with silicon IC chips makes it possible to combine the advantages of each. Among photonic devices, GaAs/AlGaAs multiple quantum well (MQW) modulators are particularly beneficial as input/output (I/O) elements on IC chips because they have a high absorption coefficient of light and can serve as both receivers and transmitters. They typically operate at an optical wavelength (.lambda.) of 850 nm (nanometers).
Growing GaAs/AlGaAs on fully-fabricated IC chips has proven difficult because it subjects the IC chips to damage. On the other hand, techniques exist for bonding fully-fabricated semiconductor devices to each other. However, these leave the substrates of each device in place. This subjects the bonds to adverse mechanical stresses that may affect the devices adversely. In the case of GaAs/AlGaAs multiple quantum well (MQW) modulators, the substrates are GaAs which are opaque to the operating wavelength of the GaAS/AlGaAs modulators, and hence require removal for operation. Nevertheless, it is very difficult to place and bond GaAs/AlGaAs multiple quantum well (MQW) modulators, if they have had their substrates removed, onto silicon IC chips.
Prior techniques for bonding fully-fabricated semiconductor devices to each other, and in particular multiple quantum well (MQW) modulators to silicon IC chips, suffer the disadvantages of mechanical stress, opacity, or cumbersome handling.
An object of the invention is to overcome these disadvantages.
Another object of the invention is to improve bonding of semiconductor devices with each other.
Another object of the invention is to improve bonding of photonic elements with electronic elements.